1. Field of the Invention
This invention relates to methyl methacrylate polymers and copolymers and especially to acrylic sheet.
2. DESCRIPTION OF THE PRIOR ART
Metal esters are known as additives to polyesters, vinyl chloride and acrylonitrile polymers, generally as thermal stabilizers, flame retardant additives and infrared absorbers. See U.S. Pat. Nos. 3,705,137; 3,647,729; 3,553,160; 3,382,209; and 3,374,200. The levels of metal used in prior polymer compositions are relatively high.
Continuously cast polymethyl methacrylate sheet is well known, but to achieve rapid casting rates it has heretofore been necessary to introduce relatively high crosslinker levels, otherwise the resultant sheet cannot be thermoformed without undesirable bubble formation. However, at these crosslinker levels the sheet looses other properties such as solvent cementability.